X-ray apparatus



w. M. LEE

X-RAY APPARATUS Nov. 10, 1953 Filed Oct. 19, 1949 2 Sheets-Sheet l INVENTOR. w/LL/AM M. LEE

Arr'x W. M. LEE

X-RAY APPARATUS Nov. 10, 1953 2 Sheets-Sheet 2 Filed Oct. 19, 1949 E R E T m L T m A @m V M o W. M A mokuuquw u Ffiik I 8 W Quwe d zwmo W B A Patented Nov. 10, 1953 William M. L ee, Delavan, 'Wis. assignor to The coniorationntrnelaware George NV. iB'ong Gorporation, Qliibalio; Ill; 12

npligationgctgher m, 1949, Serial No. 122,195

(01. 25o 'se) The present invention relates in general 179 i -ra a a atus be mere rzsrtisiiler i9 Iarr appa atu f r use n sle the a a in? swa .o the nysmiqn s t e nsvt siqn new an im r v s centra irsl is .iq s ew-fies 9 th s i ra is cc nirs .qir it are adap ss 91" 11 w th 'lir a a ar tu M11911 th X 1w tube the 'high tension transformer, and the'yalyesand qgnr .qsnss s o the vp tes ymu zt n yin .9i ii a in ta le issstns in" a noi -i oqlecd .1 d whi h t e mimar w ding o rat e .b ah ineq ality 19 the .q cci .q 2.0.00 cycles per second. The r se of HZQQO cycle cl rrent ena es smal e QIL 1IIQYS to 11s us and mak a mo s ma t t ".wise ;slit .1. the head- ,C r

saiurss .e the .sit uii howe e use ul with ot e pes of ap ara u ,A isatu b th nren is i cement d with the re ulation o ad ustmen o an le r9 1 a 'tn ,2. a i .5sa ld com rise .e ie i sinnt wh reby a P- C- voltmete qelibreted ."lsil ro s sqnns tsd to t e tout m i s altsmat r t iqu a ie tilis an is parse i i correct readings in kilov qlts nptyvithstan \sl an ss n he load in ist i. .res pLnsiYs t aqiiisimtsnt of thi mi i .se c tq An e teeters 'QXQTYPIWEK? mpisst ys or it Whifill i ssmnds t a smal ris sisis ie psd m? the win s o the a sa i th as qriinsiiyies ii sw ga wie ri ies i san w ich sn w y m sses i a .saqn- Y l 9 ci pii mies sm thelen s ii sapee s trical circuits involv ed in the invention.

Referring to'Fig. -i of "the drawing, the reference characters 1}2 and 3 indicatea three-phase power *IineQand-Sf-I is a switch for connecting the 'line through to the three-phase induction motor '8, -also=1abeled- Motor" in the drawing. E1he-relay ;6 and associated parts which are inclnded in therectanglefl eontitute a lnotorstarting and-oyerloaxioutout deviceof knownztype and construction.

'I he-gener ator-GENais preferably a single-phase alternator directlyicoupled to the motor. *It rnay have -a 1 frequency of 000 .cycles per second, {for example. andaiyariablesoutpnt voltage the :maximum value or which may the on the order of 250 volts.

t lisform is es izsd .b a r i s' i neni- 2 The tube is i satssl i9 e as 5 1% P9 :1 housing or head in- 1: isp eiisflissz sli 'isiis smi f 5 isilsi e i iis nse to the .Xw ubs. test isi s pn i ees rinsr L fer p yin arises pais iia 'w the iii-tenth n swin m' ii 1 ing circuit comprising the diodes lfi; ;9;fi 9599. ase ers 2.97.2. and th trans o m r L and $0. ,si pn n ls ss unse -is ins ,ii e is; N supplie 09 @y'sls a1 to the prima wmq i Q? the sc n imns q i s bie a sri iim s lient shown. 'The reference character 21 indicates a .vy r qes -s=ir .u i whic ,inblud igmelqirpqm t t hs psning Q wile h h u ie JJ i i esh wh ch the a mol st d init a e iranmai se y "at 1- The filt and th shutt ii ar sse sd e xs s t s 92 .8-

ii li sii iis i wa hi 2 an ias i i 9 .Wbiqh s vens; ar ,A in cate its i .sqmpri ss s skles ilsts siw i th is steep 93, s ms t s re) .t i 't h tms uma i iq einss basti- 'T T sQAain'ins i' s rs sn slssts si s l s' and it it ia 'b'fi which may be driven by an "electric motor 49 to L -his}; i i c l d the l l ys' wa '1 a th t m 4. 92 1' shutt r is sh wn i li' t n9- siti H the sl w n ii e i t e ls lsd inlets?! i i e i pses \fi q o thi loitl 31. I basi R i .9 1 .1 l ad p ate i at t right, .i' 'h ie is indicated by dotted lines. {Ifhe motor fit t ii i i is- ,1 i q an sew c is i f be PsPWlQsi szihss ii i a w l Hill wi h s i an? s4a sfs sq sis hshut e a 3 -siest -is b s s i' bar 42 carried pnfthech in 351 Whentheshiiti :i i .s;s Qs tiQ a 'i Tsiiow i h drawing, theswitchstisheld opiated'byaquiiting member ljywhile switch S3 is in 'norin'a or unoperated position. -When the 'shlitter" is opened,-the actuator 42 moves to the mmter a ting switch S4 to restore and oberating' switch S 3as the shutter reaches open position. "I he filterJQ is slidable in gnides as indicated and may be a sheetof aluminum, -for exa'rnpl e, or acomrioundsheet composed of a layer of aluminnm and layer of copper, ffor example. The filters are intei'ehangealileand a number of thein ate provided, :all different regards their-bene- =trability .by X-rays. Each filter has a contact armisuch Tas :33, and a row of contacts-AGES provided in which there is a contact individual -to each filter.

Referring to Fig. 2 of vthe drawingthe conductors 50 and 5! represent a singielphase zfifl cycle commercial power line. Switch S2 is the main switch through which 60 cycle current is supplied to the various relays and other pieces of equipment by way of the conductors 53 and 54. The reference character 5'2 indicates a voltage stabilizer by means of which current at substantially constant voltage may be supplied to certain grounded circuits which include conductor 55.

The K. V, regulator comprises a winding 55 connected between the conductor 55 and a ground and a movable contact arm 51'. It is used to regulate the anode voltage at the X-ray tube, as will be described shortly. The switch 58 is closed by the contact arm 51 when it is restored to zero position.

The reference character 59 indicates a timer of known construction. It is adapted to be set by the operator to predetermine the duration of an exposure or treatment.

The reference character 12 indicates a D. C. voltmeter which is connected to the output of the alternator GEN through the rectifier R2 and is calibrated in kilovolts. This voltmeter, re-

ferred to as the K. V. meter and so labeled in the H drawing, indicates the anode potential at the X- ray tube 30.

The load on the tube is indicated by the two anode current ammeters B9 and 8| These meters are connected to the voltage multiplying circuit over conductors 82 and 83, respectively, and are included in the respective charging circuits of the condensers 29 and 21.

The milli-ampere selector, labeled M. A. selector in the drawing, is a manually adjustable rotary switch which is used for regulating the supply of current to the filament circuit of the X-ray tube 39, which is one factor in determining the load on the tube, or the current in the anode circuit. The selector includes a contact arm 69 and may have three working positions or contacts corresponding to loads of 5, 10, and milli-amperes, respectively. These contacts are connected to adjustable taps on the resistor 6|. with the resistor 6|.

The contact arms 63, 64, and 65 are mounted on the same shaft with the contact arm 60, so that whenever contact arm 66 is adjusted the other contact arms receive a corresponding adjustment. Each contact arm has three active or working contacts, like contact arm 69.

The contact arm 63 is included in the overvoltage protective circuit, said circuit also including the potentiometer E6, the rectifier 5?, voltage regulating tube 68, and the relay 69. The tube 68 may be a Type VR105-80 tube, made by Sylvania Electric Products Co. The tube 98 is shunted by a resistor [9 which is preferably about 47M ohms. The condenser H may have a capacity of 1 mi. The operation of the circuit will be explained presently.

The contact arm 84 is operative to select a portion of the winding of the potentiometer M for inclusion in the circuit of the K. V. meter 12 in series with the output of rectifier R2. Current is supplied to the potentiometer '14 by means A vernier rheostat B2 is connected in series of the transformer 15 and the rectifier R3 and the direction of current flow is such that the voltage meter.

The contact arm 65 is included in the circuit of relay 4, Fig. 1, for a purpose to be described hereinafter.

The filter selector switch, labeled Filter Selector in the drawing, is a manuall operable rotary switch and comprises a contact arm 84 and a plurality of contacts which are connected by individual conductors to the contacts 43-46 Fig. l.

The switch S5 is a manually operable double pole switch which is provided for the purpose oi controlling the shutter 34, Fig. 1. The switch S5 has two positions, corresponding respectively to the open and closed positions of the shutter. The associated signal lamps and 86 are controlled from the shutter and indicate the open or closed position thereof as the case may be.

The operation of the equipment will now be explained, it being assumed for this purpose that the equipment is to be used for administering deep therapy to a patient. The explanation will be confined to the operation of the circuits and apparatus.

The switch SI is closed to connect up the threephase power line. The switch may be left in closed position, unless the equipment is to be taken out of service for a period, or in case the power has to be out ch to enable repairs to be made. Closure of switch SI does not start the motor, since the power circuit is open at contacts of the starting relay 8.

When the main switch S2 is closed, the power line conductors 5i and 5! are connected through to the conductors 53 and 54 and 60 cycle alternating current is supplied to the equipment, thereby energizing certain circuits with results which will be pointed out.

The first operation to which attention may be directed is the energization of relay 5, Fig. 1, which is supplied with current over conductors 9d and 9|. Upon energizing, relay 5 closes a circuit for the motor start relay 5. The latter relay accordingly energizes and closes the threephase power circuit through to the motor 8. The motor accordingl starts to run and drives the generator GEN. The generator has no power output at this time, however, for its field is not supplied with current.

The operator should now see to it that the shutter 34 is closed. Assuming that the shutter is open, switch S5 will be in its left hand position and the signal lamp 85 will be lighted. When the switch is moved to its right hand position, the lamp 85 is extinguished and a circuit is completed for the motor 40 which may be traced from conductor 54 by way of switch S5, conductor 93, switch S4 in normal position, motor 40, and conductor 94 to conductor 53. The motor 40 is accordingly operated to move the shutter 34 to its closed position. The movement of the actuating member 42 which takes place incident to the closing of the shutter restores switch S3, thereby preparing a circuit for driving the motor to open the shutter, and operates switch S4, which opens the motor circuit and stops the motor 40. The operation of switch 84 also closes circuits for lamp 86 and relay 96 which may be traced from conductor 54 by way of switch S5, conductor 93, and switch S4, in operated position, to conductor 95, and thence through lamp 86 and relay 96 in parallel to conductor 53. Lamp 86 indicates that the shutter is now closed. Re-

lay 95, upon energizing, prepares a circuit at contact 91 for energizing relay 4.

The operator may now adjust the filter selector switch to select the filter which is to be used. In this connection it will be understood that the several positions of the contact arm 84 are marked by numbersyletters. or other means for identifying the; different filters to which they correspond and the selecting: operation. consists in setting the switch. to the position which cor= responds to the desired filter. The positions may even be marked with descriptions of the filters, as 2MM. 1MM.AL-1MM1 CU,.etc.

The second position of the filter: selector switch corresponds to the-filter 32 and. the: secondfiposition contact of! the switch is connected to con! tact 44:, Fig. 1-,. by' means of. conductor 99. As suming that: the operator desires: to usexfilter. 32', he willv set the switch. 11011138 second, osition, where: it is shown in the drawing, thereby closing a. circuit which includes the grounded filter; contact arm 33 and.- contact 44,. conductor 99,. contact. arm 84, switch S6 (normally closed),-. relay $8 and the secondary winding: of transformer 81. This. is a low voltage circuit, preferably about 6-10. volts, to avoid any danger to the operator when changing filters. Upon. energizing, relay 88 closes a point in the: circuit of relay. 4 at contact. I001 The circuit is. still open, however, at the timer 59. The lamp 98 has a circuit in parallel with relay 88 and lights. at: this. time to: indicate to the operator that the desired. filter. is" in position.

It there is" no filter in position on the shutter. when the operator sets the filter selecting switch, or if a non-selected filteris. in position, the relay 88 will not energize and the lamp 88 will not. light. The failure. of the lamp to light: notifies the operator of the situation. and he. will insert the correct filter beforeattempting to proceed further.

The operator may-now adjust the milli-amperc selector to preselect the: desired value of anode current. Assuming that. a current of 5 milliamperes' istobe used; the switch is. rotated, if necessary, to set the contact arm 60 on the first contact in its bank, labeled SMA in-the. drawing. The adjustment of contact armBO' simultaneously adjusts the contact arms 83, E4, and. 65 to corresponding positions. Current. is: now flowing over a circuit which includes the primary wind.-

ing of the filament transformer L5, conductor" IOI, contact arm 60 of the milli-ampere selector. potentiometer 6Ii', Vernier. rheostat 62,. conductor: 55, and voltage stabilizer 52'. The. secondary winding of transformer I5 supplies-current. to the filament. of. the X-ray tube at apotential which will produce. the emission required for an anode current. of 5 milli-amperes; It will be understood that. the SMA tap on. the: potentiometer 6| hasbeen preadjustedto: bring about this resultand that the other-twov tapshave been preadjusted. in accordance with the indicated cur.- rent values.

The primary windings of the transformers. I3 and I4 are supplied with current through. the rheostat89i by way of conductor I02; The: sec.-

ondary windings. of. these transformers supply current to the filaments of the diodes;v It. to I9, inclusive, Fig. 1.

The operator may now set the timer 59 in.

accordance with the. length. of the. treatment to; beadministeredto the patient. Setting of. the. timer closes the switch SW; butwithout imme diate result. It closes another point. in the cir;-- cuit of. relay 4..

The next operation is the restoration of the K. V. regulator to its-zero or normal position, the circuit arrangement being such. that: this must be done before power. can. be: supplied to: the. X-ray tube When theoperator restoresthe:

6 V. regulator to zero; the contact arm 5"!- closes the switch 58,. thereby establishing a circuit for relay 4- which extends from: conductor 54 by; way of conductor I03, switch 58;. conductor H14; come tact 91 of relay 96,. conductor I105, winding. of relay 4', conductor: I06, contact I00 of relay m. contact I 01 of relay 69, conductor: H18; switch SW in the timer, conduct-or- I09,. contact arm. 05;, and conductor M0 to conductor 53'. Upomener gizing, relay 4 establishes a. locking circuit 101'. itselfwhich extends by way of contact 4-,. contact H5 of. circuit breaker 21 contact 6 of. motor start relay 6,. and conductor 90. to con ductor 54. This locking circuit. makes the eon.

tinued energization of relay 4: independent or switch 5% on the K. regulator. and. contact 81? of relay 96, since the branch 1.14, '5', I'I;0-,-.-and is in parallel with that part of the original energizing. circuit which includes I05, 9.1:, 58". and I03 When-the relay 4: energizes it closes. a grounded circuit over which alternating currentisv supplied to the rectifier RI. for energizing the field; 9? ofv the alternator GEN. This grounded-i circuit eludes the rectifier RI, conductor I:I:3.=,, contact I. |2',.COXldllCtDlf I II and the contact arm 51 of the K. regulator; The: contact arm 51' hear' ing been moved. to. its Zero: position, it: is in ensgagement with the. grounded end of the resistor and no current now takesplace in the circuit The operator will. now rotate the contact arm 51. in. a; clockwise direction, thereby opening: switch 58 and. includingia. part of the: winding of the resistor 56 in the grounded rectifier" circuit.- The opening of switch 58 has: no eifect" atthis time, since relay 4 is held energized over its locking circuit. But it does insure that when ever relay 4 is deenergi'zed it cannotagain be energized. except by restoring the K V, regulator to. zero position.

The operation of'the K. V. regulator-supplies alternating current to rectifier RI, which suppliesdirect currentto" the field 9 of the alternator; The alternator voltage builds up quicklyand-200 0 cycle alternating current is supplied to the pri-' mary winding of the-higli' tension transformer I? inthei voltage multiplying circuit. The operation of the latter circuit will not be discussed d'e tail. since it" is known and isnot involved in the invention. Suifice-it-t'o say that thevoltage generat'ed' in the secondary Winding of transformer I2 is multiplied approximately four times and is applied to the anode circuit of the X-ray' tube! This circuit includes the conductors I20 and IZI, leading to" the cathode and anode, respectively, of theX-ray tube.

Thealternator also suppliescurrent overrco'nductor 13- to the-rectifier R2 and to the potentiometer 65, Fig. 2. The direct current output of the rectifier R2 isconnected to the K. V. meter in serieswith the contact arm 64' and a part of the winding of the potentiometer; The potentiometer is supplied with current'at this time by the transformer I5 and rectifier R3, and the: di-

, rection of current flow is suchthat the upper'and lower ends of thepotentiometerare negative: and positive, respectively. Rectifier R2 having the polarities as shown, it follows that the voltage developed across that portion of the potentiometer which is in series-with the K. V. meter will oppose the voltage of the rectifier R2. .This'opposing voltage is small as compared to-the vo'lt age of the alternator. The voltage across the entire potentiometer may be on the order? of about 20 volts, for example:

' As" previously mentioned, the alternator supplies current over conductor 13 to the potentiometer 66, which is connected in parallel with the rectifier R2. There will accordingly be a potential at the tap I30 of the potentiometer which causes an intermittent current flow by way of said tap, the contact arm 63, rectifier 61, resistor 10, and the relay 69 to ground. Due to the high resistance of resistor I'll, the relay 69 is not energized. The condenser II becomes charged, however, and the tap I30 is so adjusted that the potential at the condenser is only a few volts lower than the breakdown or firing potential of the tube 68. If the breakdown potential is 105 volts, the potential at the condenser may be 100 volts, so that a rise in potential of volts will cause the tube to fire.

' It will be seen that the K. V. meter will respond directly to changes in the voltage of the alternator, being connected to the alternator output in the manner explained. The anode voltage at the X-ray tube is a function of the alternator voltage, however, and hence the meter may be calibrated in kilovolts, to show directly the voltage at the tube, or between conductors I20 and I2 I. The calibration is carried out by known methods which need not be explained herein. In case the calibration is affected subsequently by replacement of parts in the head it can be corrected by adjusting the movable tap I25.

The operator observes the K. V. meter and notes the reading thereof. It may be assumed by way of example that the maximum anode voltage that can be used is 250 kilovolts and that the treatment is to be given at the maximum voltage. The operator accordingly will rotate the contact arm 51 of the K. V. regulator until the K. V. meter indicates 250 kilovolts.

The operator should also observe the anode current ammeters 80 and 8I at this time, to see if the readings correspond to the setting of the milli-ampere selector switch. This switch has been set for 5 milli-amperes and the reading of the K. V. meter will not be correct unless the current actually has this value. more or less than 5 milli-amperes, therefore, the necessary correction is made by adjusting the rheostat 62.

It may be noted at this point that resetting of the milli-ampere selector at this stage is not permissible. If the operator should forget this, and adjust the selector to some different load than the load for which it was previously set, the movement of contact arm 65 will break the circuit of relay 4. This relay will then deenergize and stop the supply of current to the field of the alternator. The operation can proceed at the new setting but in order to do so the operator has to start over again by restoring the K. V. regulator to zero.

. The equipment is now ready, and the next operation is to open the shutter and start the treatment. This is accomplished by moving the switch S5 to its left hand or Open position.

The operation of switch S5 opens the circuit for lamp 85 and the relay 96. The lamp is accordingly extinguished and relay 96 is deenergized. Contact 91 of relay 96 is thus opened but relay 4 remains energized over its locking circuit.

The operation of switch S5 also closes a circuit for the motor 46 which can be traced from conductor 54 by way of left hand contact arm of the switch, conductor 92, switch S3, motor 4% and conductor 94 to conductor 53. The motor 40 accordingly starts to run and moves the shut ter 34 to its open position, shown in dotted lines If the current is inthe drawing. The opening of the shutter is accompanied by the movement of actuator 42, which permits switch S4 to restore and operates switch S3. The latter switch opens the motor circuit to stop the motor and closes a circuit for the lamp 85. The lighting of lamp indicates to the operator that the shutter is open and that the treatment has begun.

The movement of switch S5 to its left hand position also closes a circuit for the motor in the timer 59, said circuit extending from conductor 53 by way of right hand contact arm of switch S5, conductor I26, timer motor to conductor I05, and thence by way of the locking circuit of relay 4 to conductor 54. The timer is now in operation and starts to measure off the time interval for which it has been set.

Upon the expiration of the time interval, the timer opens the switch SW, thereby breaking the circuit of relay 4, Fig. 1. Upon deenergizing, relay 1i breaks its locking circuit at contact II4 and at contact II2 breaks the circuit over which current is supplied to rectifier R4 for energizing the field of the alternator GEN. The generator output then falls to zero and the generation of X-rays ceases.

In case of an emergency occuring during th treatment, the operator can stop the treatment instantly by momentarily opening the switch S6. This switch opens the circuit of relay 88, which falls back and opens the circuit of relay 4. It will be noted that if the relay 4 is deenergized in the course of a treatment, it cannot be energized again without first closing the shutter 34 and energizing relay 96 to prepare the initial energizing circuit of relay 4 by way of switch 58 at the K. V. regulator.

It will be assumed now that another treatment is to be given, with the voltage the same as before, that is, 250 kilovolts, and with an anode current of 10 milli-amperes.

The operator will proceed as before, first moving switch S5 to its right hand position to close the shutter, then adjusting the filter selector, if necessary, resetting the M. A. selector, and setting the timer. The resetting of the M. A. selector moves the contact arm 69 to the contact labeled 10 MA and at the same time the contact arms 63 and 64 are moved to contacts HI and I25, respectively.

The restoration of the K. V. regulator to zero closes switch 58 to energize relay 4, which locks itself and prepares the circuit for supplying current to the field of the alternator. Rotation of the contact arm 51 of the K. V. regulator closes this circuit, whereupon the alternator builds up voltage promptly and begins to supply current to the X-ray tube. As in the case previously described, the operator will rotate the arm 51 of the K. V. regulator in a clockwise direction, increasing the field current at the alternator until the K. V. meter shows the desired anode voltage,

or 250 kilovolts.

The operator can rely on the voltage at the X-ray tube being 250 kilovolts, as indicated by the K. V. meter, notwithstanding the increase in the load from 5 milli-amperes to 10 milli-amperes, because the voltage of the alternator has been increased sufficiently to compensate for the losses resulting from the increase in the load.

Explaining this further, the opposing voltage in the circuit of the K. V. meter is greater now than it was in the former case, due to the movement of contact arm 54 from the contact connected to the tap I25 to the contact connected the alternator must be raised to a highervalue than before in order to bring the reading of The tap the K. V. meter up to 250 kilovolts. 126 is so adjusted that when the load on the tube is 10 milliamperes the value of the opposing voltage at the tap is sufiicient to-efiect'thenecea sary compensation and make the calibration of the K. V. meter correct for that load.

The tap I2! is adjusted so as to make the necessary compensation for a load of 15 milliamperes.

It will be recalled now that tap I30 on potentiometer 66 is so adjusted that when the-load on the X-ray tube is 5 milli-amperes the potential at the condenser H is preferably about 100 volts, assuming that the breakdown potential of the tube 68 is 105 volts. When the load is changed to milli-amperes and the anode potential is brought up to 250 kilovolts, the alternator voltage is higher than before, for the reasons explained, which raises the potential at tap I30 close'to or above the breakdown potential of tube 68, or 105 volts. However, the contact arm '63 is now in engagement with the contact which is connected to tap l3l, which is so adjusted that the voltage at the condenser H is still only 100 volts, notwithstanding the increase in the alternator voltage.

The tap I32 is so adjusted that when the milli-ampere selector is adjusted for a current of milli-amperes, and the voltage at the tube is brought up to 250 kilovolts, the potential at the condenser H will be 100 volts.

The overvoltage protective circuit makes it possible to maintain a close supervision of the equipment when the maximum voltage of 250,000 kilovolts is employed, in spite of the variations in the alternator voltage which are required in order to maintain the tube voltage at the desired value under different load conditions;

In case the voltage at the condenser H should rise to a value equal to the breakdown potential of tube 68, the tube will fire and the condenser H will discharge through relay 69. Upon energizing, relay 69 breaks the circuit of relay 4 at contact I01 and the latter relay deenergizes to interrupt the supply of field current to the alternator in the manner already explained.

The invention having been described that which is believed to be new and for which the protection of Letters Patent is desired will be pointed out in the appended claims.

I claim:

1. In combination, an X-ray tube, means including an alternator for supplying power to said tube, a circuit for supplying current tothe field oi saidalternator, a regulator for adjusting the current flow in said circuit to regulate the voltage of said alternator, said regulator including a normally open switch which is closed responsive to an operation of said regulator which would reduce the current fiow in said circuit, if current were fiowing therein, a control relay for closing said circuit, an initial energizing circuit for said relay including said switch, and a looking circuit for said relay independent of said switch, said locking circuit including contacts closed by said relay on energizing.

2. The combination as claimed in claim 1, including a shutter for the X-ray tube, a relay energized responsive to closure of said shutter, and contacts on said relay which are included in the initial energizing circuit of the control relay in series with the said switch at the regulator.

3. The combination as claimed in claim 1,.including a milli-ampere selector switch for controlling the load on said tube, and means for opening the relay locking circuit in response to adjustment of said selector switch to change the load, said means comprising a switch actuated by said selector switch during said adjustment.

4. In combination, an X-ray tube, a relay for controlling the supply of power to the anode circuit of said tube, a milli-ampere selector. for controlling the load on said tube, means including a circuit and switch therein for energizing. said relay, a locking circuit for maintaining said relay energized independent of said switch, said looking circuit including normally open contacts on said relay, and means for opening said locking circuit to deenergize said relay in response to any change in the setting of said selector switch, said last means comprising a contact arm of said switch and spaced contacts engaged thereby which are included in said locking circuit.

5. In combination, an X-ray tube, a control relay controlling the supply of power to the anode circuit of said tube, a circuit including saidrelay,

a power voltage regulator, a switch actuated responsive to adjustment of said regulator to a starting position to close said circuit and energize said relay, a locking circuit including contacts'oi said relay to maintain the same energized when said regulator is moved to various working positions to increase the voltage, a timer having a switch and means for opening it after a predetermined time interval, said timer switch being included in said locking circuit, and means for starting said timer.

6. The combination claimed in claim 5, including an emergency switch for opening saidlocking circuit independent of said timer.

7. The combination claimed in claim 5, including a circuit breaker for opening said locking circuit responsive to an excessive consumption of power by said tube.

8. The combination claimed in claim 5,. including a shutter for the X-ray tube, and means for preventing the energization of said relay unless said shutter is closed, said last means comprising a second relay energized by closure of said shutter, and normally open contacts on said second relay connected in the circuit of said first relay.

9. The combination as claimed in claim 5, including a motor for driving the timer, and a circuit for said motor extending through contacts in the locking circuit closed by said relay when energized.

10. In combination, an X-ray tube, a shutter for said tube, a first relay energized responsive to closing said shutter, a filter selector, a second relay energized responsive to placing a selected filter in position adjacent said shutter, a third relay controlling the supply of power to said tube, an initial energizing circuit for said third relay including contacts of said first and second relays in series, and a locking circuit for maintaining said third relay energized when said shutter is open and said first relay is deenergized, said locking circuit including the said contacts on said second relay but not the contacts on said first relay.

11. In combination, an X-ray tube, means including a transformer for supplying a high voltage to the anode circuit of said tube, an alternator for supplying current to the primary winding of said transformer, a rectifier, a direct current voltmeter connected to the output of said alternator through said rectifier, said voltmeter being calibrated in kilovolts to indicate the anode voltage at said tube, a milli-ampere selector switch having a contact arm and associated bank of contacts for controlling the load on said tube, a source of direct current supplying a variable voltage in the circuit of said voltmeter in opposition to the voltage supplied by said alternator, means included in said milli-ampere selector switch for changing the value of said variable voltage in accordance with changes in the load, said last means including a second contact arm and associated bank of contacts, and means for regulating the voltage of said alternator,

12. The combination as claimed in claim 11, together with independently adjustable means for changing the value of said variable voltage, said means comprising a potentiometer having adjustable taps which are connected to contacts in the second bank of contacts in said selector switch.

13. In combination, an X-ray tube, means including a transformer for supplying a high voltage to the anode circuit of said tube, an alternator for supplying current to the primary winding of said transformer, a rectifier, a direct current voltmeter connected to the output of said alternator through said rectifier, said voltmeter being calibrated in kilovolts to indicate the anode voltage at said tube, a milli-ampere selector switch for controlling the load on said tube, a source of alternating current differing in frequency from the frequency of said alternator, means including said source and a second rectifier for introducing a variable voltage in the circuit of said voltmeter in opposition to the voltage supplied through the first said rectifier by said alternator, a switch mechanically coupled to said milli-ampere selector switch, means including said second switch for effecting predetermined changes in the value of said variable voltage responsive to the operation of said milli-ampere selector switch to effect changes in the load on said tube, and means for regulating the voltage of said alternator.

14. The combination as claimed in claim 13, wherein the means for effecting predetermined changes in the value of the variable voltage includes a potentiometer and independently adjustable taps which are selectable by the second switch.

15. In combination, an X-ray tube, means including a transformer and a source of alternating current for supplying a high voltage to the anode circuit of said tube, a milli-ampere selector switch for controlling the load on said tube, means for changing the voltage of said source in accordance with changes in the load, a diode space discharge tube having a fixed breakdown potential, a protective circuit including a relay connected across said source in series with said discharge tube, said relay having means for controlling the supply of current to the anode circuit of said X-ray tube, a variable resistance in said protective circuit, means including said resistance for regulating the voltage between the cathode and anode of said discharge tube to a selected value which is less than said breakdown potential, switching means responsive to adjustment of said selector switch for maintaining the voltage at said discharge tube substantially constant at said selected value notwithstanding changes in the voltage of said source made pursuant to changes in the load, and connections between said resistance and said switch whereby said switch adjusts the amount of said resistance in said protective circuit to control the voltage at said discharge tube as set forth.

16. In combination, an X-ray tube, means including a transformer and a source of alternating current for supplying a high voltage to the anode circuit of said tube, a milli-ampere selector switch for controlling the load on said tube, means for changing the voltage of said source in accordance with changes in the load, a potentiometer connected across the terminals of said source, said potentiometer having a plurality of adjustable taps, a second switch having bank contacts connected to said taps, respectively, a diode space discharge tube having a fixed breakdown potential, a protective circuit including said switch and said discharge tube connected in series between said potentiometer and one terminal of said source, the voltage at said discharge tube being regulated to a selected value less than said breakdown potential by adjustment of said potentiometer, a mechanical connection to operate said second switch responsive to operation of said milliampere selector switch, a relay insaid protective circuit energized by breakdown of said discharge tube, and means controlled by said relay to interrupt the supply of current to the anode circuit of said X-ray tube.

WILLIAM M. LEE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,094,103 Horsely et al Sept. 28, 1937 2,193,071 Lee Mar. 12, 1940 2,339,902 Akers et al Jan. 25, 1944 2,368,798 Ball Feb. 6, 1945 2,477,298 Goldfield July 26, 1949 2,488,167 Brown Nov. 15, 1949 2,488,168 Brown Nov. 15, 1949 2,492,281 Hall Dec. 27, 1949 2,494,218 Weisglass Jan. 10, 1950 

